1. Field of the Invention
This invention relates to reusable self-locking fasteners and in particular relates to metallic threaded fasteners utilizing a metallic patch to provide the locking characteristic.
2. Description of the Prior Art
A variety of self-locking threaded fasteners have been utilized in the past. One type of prior art self-locking fastener utilized a plastic patch and the elastic memory of the plastic material to maintain an adequate locking torque over a number of reuses of the fastener. While these plastic patch fasteners have been generally satisfactory in some usage, their usage has been somewhat limited or impaired by the relatively low modulus of elasticity of the plastic patch, causing the patch to provide only a limited locking torque, by their relatively poor performance in high temperature environments or in applications involving the use of certain organic fluids (e.g. solvents), and by the tendency of the plastic patch to cut. In particular, there has been heretofore a long-felt need for an improved self-locking fastener having an improved reusability characteristic, a high locking torque and/or having the ability to perform well at high temperatures, and/or in the presence of organic fluids.
Another type of prior art self-locking fastener involved the use of a plated metallic path harder than at least one of the corresponding threaded members. These types of hard metallic patch fasteners, such as may be seen in Bergere U.S. Pat. No. 3,552,467, operate by deforming at least one of the mating threaded members. While these fasteners are satisfactory for some uses if properly sized and if utilized with an easily deformable member, such as a nut, they will tend to permanently deform or destroy the threaded members if utilized with a relatively undeformable member such as a threaded engine block or if the patch is oversized.
Another type of prior art self-locking fastener utilized a relatively soft metallic coating on the threaded surface. This type of fastener such as is shown in Woodward U.S. Pat. No. 1,368,087 tended to provide relatively low locking torque and also tended to be relatively poor for repeated applications as the coating would tend to simply extrude after the first on-off cycle.
In summary, of all of the prior art known to applicant, none provides a self-locking fastener which is capable of reuse without losing its locking characteristics and which is substantially non-destructive to the threaded members and has the ability to perform well at high temperatures and/or in the presence of organic fluids. The need for such an improved self-locking fastener is obvious and the present invention is directed to the provision of such a fastener.